Turn on sparse index and remove ensure_full_index().
Before this patch, `git-grep` utilizes the ensure_full_index() method to
expand the index and search all the entries. Because this method
requires walking all the trees and constructing the index, it is the
slow part within the whole command.
To achieve better performance, this patch uses grep_tree() to search the
sparse directory entries and get rid of the ensure_full_index() method.
Why grep_tree() is a better choice over ensure_full_index()?
1) grep_tree() is as correct as ensure_full_index(). grep_tree() looks
into every sparse-directory entry (represented by a tree) recursively
when looping over the index, and the result of doing so matches the
result of expanding the index.
2) grep_tree() utilizes pathspecs to limit the scope of searching.
ensure_full_index() always expands the index, which means it will
always walk all the trees and blobs in the repo without caring if
the user only wants a subset of the content, i.e. using a pathspec.
On the other hand, grep_tree() will only search the contents that
match the pathspec, and thus possibly walking fewer trees.
3) grep_tree() does not construct and copy back a new index, while
ensure_full_index() does. This also saves some time.
----------------
Performance test
- Summary:
p2000 tests demonstrate a ~71% execution time reduction for
`git grep --cached bogus -- "f2/f1/f1/*"` using tree-walking logic.
However, notice that this result varies depending on the pathspec
given. See below "Command used for testing" for more details.
Test HEAD~ HEAD
-------------------------------------------------------
2000.78: git grep ... (full-v3) 0.35 0.39 (≈)
2000.79: git grep ... (full-v4) 0.36 0.30 (≈)
2000.80: git grep ... (sparse-v3) 0.88 0.23 (-73.8%)
2000.81: git grep ... (sparse-v4) 0.83 0.26 (-68.6%)
- Command used for testing:
git grep --cached bogus -- "f2/f1/f1/*"
The reason for specifying a pathspec is that, if we don't specify a
pathspec, then grep_tree() will walk all the trees and blobs to find the
pattern, and the time consumed doing so is not too different from using
the original ensure_full_index() method, which also spends most of the
time walking trees. However, when a pathspec is specified, this latest
logic will only walk the area of trees enclosed by the pathspec, and the
time consumed is reasonably a lot less.
Generally speaking, because the performance gain is acheived by walking
less trees, which are specified by the pathspec, the HEAD time v.s.
HEAD~ time in sparse-v[3|4], should be proportional to
"pathspec enclosed area" v.s. "all area", respectively. Namely, the
wider the <pathspec> is encompassing, the less the performance
difference between HEAD~ and HEAD, and vice versa.
That is, if we don't specify a pathspec, the performance difference [1]
is indistinguishable: both methods walk all the trees and take generally
same amount of time (even with the index construction time included for
ensure_full_index()).
[1] Performance test result without pathspec (hence walking all trees):
Command used:
git grep --cached bogus
Test HEAD~ HEAD
---------------------------------------------------
2000.78: git grep ... (full-v3) 6.17 5.19 (≈)
2000.79: git grep ... (full-v4) 6.19 5.46 (≈)
2000.80: git grep ... (sparse-v3) 6.57 6.44 (≈)
2000.81: git grep ... (sparse-v4) 6.65 6.28 (≈)
--------------------------
NEEDSWORK about submodules
There are a few NEEDSWORKs that belong to improvements beyond this
topic. See the NEEDSWORK in builtin/grep.c::grep_submodule() for
more context. The other two NEEDSWORKs in t1092 are also relative.
Suggested-by: Derrick Stolee <derrickstolee@github.com>
Helped-by: Derrick Stolee <derrickstolee@github.com>
Helped-by: Victoria Dye <vdye@github.com>
Helped-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Shaoxuan Yuan <shaoxuan.yuan02@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Enable the sparse index within the `git-rm` command.
The `p2000` tests demonstrate a ~92% execution time reduction for
'git rm' using a sparse index.
Test HEAD~1 HEAD
--------------------------------------------------------------------------
2000.74: git rm ... (full-v3) 0.41(0.37+0.05) 0.43(0.36+0.07) +4.9%
2000.75: git rm ... (full-v4) 0.38(0.34+0.05) 0.39(0.35+0.05) +2.6%
2000.76: git rm ... (sparse-v3) 0.57(0.56+0.01) 0.05(0.05+0.00) -91.2%
2000.77: git rm ... (sparse-v4) 0.57(0.55+0.02) 0.03(0.03+0.00) -94.7%
----
Also, normalize a behavioral difference of `git-rm` under sparse-index.
See related discussion [1].
`git-rm` a sparse-directory entry within a sparse-index enabled repo
behaves differently from a sparse directory within a sparse-checkout
enabled repo.
For example, in a sparse-index repo, where 'folder1' is a
sparse-directory entry, `git rm -r --sparse folder1` provides this:
rm 'folder1/'
Whereas in a sparse-checkout repo *without* sparse-index, doing so
provides this:
rm 'folder1/0/0/0'
rm 'folder1/0/1'
rm 'folder1/a'
Because `git rm` a sparse-directory entry does not need to expand the
index, therefore we should accept the current behavior, which is faster
than "expand the sparse-directory entry to match the sparse-checkout
situation".
Modify a previous test so such difference is not considered as an error.
[1] https://github.com/ffyuanda/git/pull/6#discussion_r934861398
Helped-by: Victoria Dye <vdye@github.com>
Helped-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Shaoxuan Yuan <shaoxuan.yuan02@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
"sparse-checkout" learns to work well with the sparse-index
feature.
* ds/sparse-sparse-checkout:
sparse-checkout: integrate with sparse index
p2000: add test for 'git sparse-checkout [add|set]'
sparse-index: complete partial expansion
sparse-index: partially expand directories
sparse-checkout: --no-sparse-index needs a full index
cache-tree: implement cache_tree_find_path()
sparse-index: introduce partially-sparse indexes
sparse-index: create expand_index()
t1092: stress test 'git sparse-checkout set'
t1092: refactor 'sparse-index contents' test
The sparse-checkout builtin is almost completely integrated with the
sparse index, allowing the sparse-checkout boundary to be modified
without expanding a sparse index to a full one. Add a test to
p2000-sparse-operations.sh that adds a directory to the sparse-checkout
definition, then removes it. Using both operations is important to
ensure that the operation is doing the same work in each repetition as
well as leaving the test repo in a good state for later tests.
Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add tests verifying expected 'git stash' behavior in
't1092-sparse-checkout-compatibility'. These cases establish the expected
behavior of 'git stash' in a sparse-checkout and verify consistency both
with and without a sparse index. Although no sparse index compatibility has
been integrated into 'git stash' yet, the tests are all 'expect_success' -
we don't want the cone-mode sparse-checkout behavior to change depending on
whether it is using a sparse index or not. Therefore, we expect these tests
to continue passing once sparse index is integrated with 'git stash'.
Additionally, add performance test cases for 'git stash' both with and
without untracked files. Note that, unlike the other tests in
'p2000-sparse-operations.sh', the tests added for 'stash' are combination
operations. This is done to ensure the stash/unstash is not blocked by the
modification of '$SPARSE_CONE/a' performed as part of 'test_perf_on_all'.
Signed-off-by: Victoria Dye <vdye@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add tests focused on how 'git read-tree' behaves in sparse checkouts. Extra
emphasis is placed on interactions with files outside the sparse cone, e.g.
merges with out-of-cone conflicts.
Helped-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Victoria Dye <vdye@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Introduce tests for a variety of `git update-index` use cases, including
performance scenarios. Tests are intended to exercise `update-index` with
options that change the commands interaction with the index (e.g.,
`--again`) and with files/directories inside and outside a sparse checkout
cone.
Of note is that these tests clearly establish the behavior of `git
update-index --add` with untracked, outside-of-cone files. Unlike `git add`,
which fails with an error when provided with such files, `update-index`
succeeds in adding them to the index. Additionally, the `skip-worktree` flag
is *not* automatically added to the new entry. Although this is pre-existing
behavior, there are a couple of reasons to avoid changing it in favor of
consistency with e.g. `git add`:
* `update-index` is low-level command for modifying the index; while it can
perform operations similar to those of `add`, it traditionally has fewer
"guardrails" preventing a user from doing something they may not want to
do (in this case, adding an outside-of-cone, non-`skip-worktree` file to
the index)
* `update-index` typically only exits with an error code if it is incapable
of performing an operation (e.g., if an internal function call fails);
adding a new file outside the sparse checkout definition is still a valid
operation, albeit an inadvisable one
* `update-index` does not implicitly set flags (e.g., `skip-worktree`) when
creating new index entries with `--add`; if flags need to be updated,
options like `--[no-]skip-worktree` allow a user to intentionally set them
All this to say that, while there are valid reasons to consider changing the
treatment of outside-of-cone files in `update-index`, there are also
sufficient reasons for leaving it as-is.
Co-authored-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Victoria Dye <vdye@github.com>
Reviewed-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add tests to cover `checkout-index`, with a focus on cases interesting in a
sparse checkout (e.g., files specified outside sparse checkout definition).
New tests are intended to serve as a baseline for existing and/or expected
behavior and performance when integrating `checkout-index` with the sparse
index. Note that the test 'checkout-index --all' is marked as
'test_expect_failure', indicating that `update-index --all` will be modified
in a subsequent patch to behave as the test expects.
Signed-off-by: Victoria Dye <vdye@github.com>
Reviewed-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Enable the sparse index for the 'git blame' command. The index was already
not expanded with this command, so the most interesting thing to do is to
add tests that verify that 'git blame' behaves correctly when the sparse
index is enabled and that its performance improves. More specifically, these
cases are:
1. The index is not expanded for 'blame' when given paths in the sparse
checkout cone at multiple levels.
2. Performance measurably improves for 'blame' with sparse index when given
paths in the sparse checkout cone at multiple levels.
The `p2000` tests demonstrate a ~60% execution time reduction when running
'blame' for a file two levels deep and and a ~30% execution time reduction
for a file three levels deep.
Test before after
----------------------------------------------------------------
2000.62: git blame f2/f4/a (full-v3) 0.31 0.32 +3.2%
2000.63: git blame f2/f4/a (full-v4) 0.29 0.31 +6.9%
2000.64: git blame f2/f4/a (sparse-v3) 0.55 0.23 -58.2%
2000.65: git blame f2/f4/a (sparse-v4) 0.57 0.23 -59.6%
2000.66: git blame f2/f4/f3/a (full-v3) 0.77 0.85 +10.4%
2000.67: git blame f2/f4/f3/a (full-v4) 0.78 0.81 +3.8%
2000.68: git blame f2/f4/f3/a (sparse-v3) 1.07 0.72 -32.7%
2000.99: git blame f2/f4/f3/a (sparse-v4) 1.05 0.73 -30.5%
We do not include paths outside the sparse checkout cone because blame
does not support blaming files that are not present in the working
directory. This is true in both sparse and full checkouts.
Signed-off-by: Lessley Dennington <lessleydennington@gmail.com>
Reviewed-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Enable the sparse index within the 'git diff' command. Its implementation
already safely integrates with the sparse index because it shares code
with the 'git status' and 'git checkout' commands that were already
integrated. For more details see:
d76723ee53 (status: use sparse-index throughout, 2021-07-14)
1ba5f45132 (checkout: stop expanding sparse indexes, 2021-06-29)
The most interesting thing to do is to add tests that verify that 'git
diff' behaves correctly when the sparse index is enabled. These cases are:
1. The index is not expanded for 'diff' and 'diff --staged'
2. 'diff' and 'diff --staged' behave the same in full checkout, sparse
checkout, and sparse index repositories in the following partially-staged
scenarios (i.e. the index, HEAD, and working directory differ at a given
path):
1. Path is within sparse-checkout cone
2. Path is outside sparse-checkout cone
3. A merge conflict exists for paths outside sparse-checkout cone
The `p2000` tests demonstrate a ~44% execution time reduction for 'git
diff' and a ~86% execution time reduction for 'git diff --staged' using a
sparse index:
Test before after
-------------------------------------------------------------
2000.30: git diff (full-v3) 0.33 0.34 +3.0%
2000.31: git diff (full-v4) 0.33 0.35 +6.1%
2000.32: git diff (sparse-v3) 0.53 0.31 -41.5%
2000.33: git diff (sparse-v4) 0.54 0.29 -46.3%
2000.34: git diff --cached (full-v3) 0.07 0.07 +0.0%
2000.35: git diff --cached (full-v4) 0.07 0.08 +14.3%
2000.36: git diff --cached (sparse-v3) 0.28 0.04 -85.7%
2000.37: git diff --cached (sparse-v4) 0.23 0.03 -87.0%
Co-authored-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Lessley Dennington <lessleydennington@gmail.com>
Reviewed-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add new tests for `--merge` and `--keep` modes, as well as mixed reset with
pathspecs. New performance test cases exercise various execution paths for
`reset`.
Co-authored-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Victoria Dye <vdye@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
By using shorter names for the test repos, we will get a slightly more
compressed performance summary without comprimising clarity.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
As we increase our list of commands to test in
p2000-sparse-operations.sh, we will want to have a slightly smaller test
repository. Reduce the size by a factor of four by reducing the depth of
the step that creates a big index around a moderately-sized repository.
Also add a step to run 'git checkout -' on repeat. This requires having
a previous location in the reflog, so add that to the initialization
steps.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
p2000-sparse-operations.sh compares different Git commands in
repositories with many files at HEAD but using sparse-checkout to focus
on a small portion of those files.
Add extra copies of the repository that use the sparse-index format so
we can track how that affects the performance of different commands.
At this point in time, the sparse-index is 100% overhead from the CPU
front, and this is measurable in these tests:
Test
---------------------------------------------------------------
2000.2: git status (full-index-v3) 0.59(0.51+0.12)
2000.3: git status (full-index-v4) 0.59(0.52+0.11)
2000.4: git status (sparse-index-v3) 1.40(1.32+0.12)
2000.5: git status (sparse-index-v4) 1.41(1.36+0.08)
2000.6: git add -A (full-index-v3) 2.32(1.97+0.19)
2000.7: git add -A (full-index-v4) 2.17(1.92+0.14)
2000.8: git add -A (sparse-index-v3) 2.31(2.21+0.15)
2000.9: git add -A (sparse-index-v4) 2.30(2.20+0.13)
2000.10: git add . (full-index-v3) 2.39(2.02+0.20)
2000.11: git add . (full-index-v4) 2.20(1.94+0.16)
2000.12: git add . (sparse-index-v3) 2.36(2.27+0.12)
2000.13: git add . (sparse-index-v4) 2.33(2.21+0.16)
2000.14: git commit -a -m A (full-index-v3) 2.47(2.12+0.20)
2000.15: git commit -a -m A (full-index-v4) 2.26(2.00+0.17)
2000.16: git commit -a -m A (sparse-index-v3) 3.01(2.92+0.16)
2000.17: git commit -a -m A (sparse-index-v4) 3.01(2.94+0.15)
Note that there is very little difference between the v3 and v4 index
formats when the sparse-index is enabled. This is primarily due to the
fact that the relative file sizes are the same, and the command time is
mostly taken up by parsing tree objects to expand the sparse index into
a full one.
With the current file layout, the index file sizes are given by this
table:
| full index | sparse index |
+-------------+--------------+
v3 | 108 MiB | 1.6 MiB |
v4 | 80 MiB | 1.2 MiB |
Future updates will improve the performance of Git commands when the
index is sparse.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Create a test script that takes the default performance test (the Git
codebase) and multiplies it by 256 using four layers of duplicated
trees of width four. This results in nearly one million blob entries in
the index. Then, we can clone this repository with sparse-checkout
patterns that demonstrate four copies of the initial repository. Each
clone will use a different index format or mode so peformance can be
tested across the different options.
Note that the initial repo is stripped of submodules before doing the
copies. This preserves the expected data shape of the sparse index,
because directories containing submodules are not collapsed to a sparse
directory entry.
Run a few Git commands on these clones, especially those that use the
index (status, add, commit).
Here are the results on my Linux machine:
Test
--------------------------------------------------------------
2000.2: git status (full-index-v3) 0.37(0.30+0.09)
2000.3: git status (full-index-v4) 0.39(0.32+0.10)
2000.4: git add -A (full-index-v3) 1.42(1.06+0.20)
2000.5: git add -A (full-index-v4) 1.26(0.98+0.16)
2000.6: git add . (full-index-v3) 1.40(1.04+0.18)
2000.7: git add . (full-index-v4) 1.26(0.98+0.17)
2000.8: git commit -a -m A (full-index-v3) 1.42(1.11+0.16)
2000.9: git commit -a -m A (full-index-v4) 1.33(1.08+0.16)
It is perhaps noteworthy that there is an improvement when using index
version 4. This is because the v3 index uses 108 MiB while the v4
index uses 80 MiB. Since the repeated portions of the directories are
very short (f3/f1/f2, for example) this ratio is less pronounced than in
similarly-sized real repositories.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
